Clarify wording in web interface about domains without email enabled

[fulax]

On a AlternC account with domains having gesmx=0 (email disabled), when I go to "Sympa Mailing lists" menu, the interface says:

No domain is installed on your account, you cannot create any mailing list!

It should says something more alike

No domain with email enabled on your account

So I can understand I forgot to enable emails.